Allergy sufferers' red, itchy, watery eyes may in part be a response triggered by an allergic response of the nose.

As Reuters Health reports, the nasonasal reflex, in which an allergen introduced into one nostril causes the other nostril to respond in kind, has been demonstrated previously. Because the eyes and the nasal cavity share the same nerve supply, researchers thought that eye allergies occurred not only from direct exposure to allergens, but also due to a similar reflex response.

Indeed, research demonstrated that histamine release in the nose does in fact trigger eye allergies. This means that the pollen or other allergens you inhale are most likely the culprit in your eye allergy symptoms; while some allergen does probably get into your eye directly, this amount is much smaller than the amount you inhale.

In further corroboration of these findings, corticosteroids that are delivered through the nasal passages can also reduce eye allergy symptoms.

Dr. Fuad M. Baroody and his colleagues at the University of Chicago reported their findings in the Annals of Allergy, Asthma & Immunology. The researchers conclude, "The eye symptoms associated with allergic rhinities probably arise, in part, from a naso-ocular reflex."